There are many uses for thermally insulated metal tubes. For example, internal combustion engine exhaust systems having catalytic converters operate more efficiently when the exhaust gases fed to the converter are at a relatively high temperature. The engine exhaust pipe or tube between the exhaust manifold and the coverter thus is preferably insulated to maintain the exhaust gas temperatures sufficiently high to provide the higher efficiency of the converter. Ceramics have a relatively low thermal conductivity and high temperature resistance and would appear to provide a good material for such a usage. However, ceramics have a considerably different coefficient of thermal expansion than metals and are relatively brittle so that the ceramic would break or crack if used for such a purpose. If the ceramic were used in a fibrous structure rather than a monolithic structure, the fibers would not be sufficiently strong to withstand the high velocity and the pulsating action of exhaust gases moving through the tube. Also, another problem with manufacturing exhaust tubes for use with internal combustion engines is that these tubes are not straight and the bent shape thereof makes it relatively difficult to line the tube. It is also desirable for such tubes to provide noise insulation.